A printing unit for printing on one surface and the other surface of a continuous web using ink jet printing devices is disclosed in Japanese Unexamined Patent Publication No. He. 11-320923 (related art 1), Japanese Unexamined Patent Publication No. 2001-58446 (related art 2) and Japanese Unexamined Patent Publication No. 2003-11452 (related art 3). A production method for newspapers using a digital printing device including an ink jet printing unit is disclosed in Japanese Unexamined Patent Publication No. 2003-341927 (related art 4).
The printing unit for printing on one surface and the other surface of a continuous web disclosed in related art 1 and related art 2 has an ink jet printing unit with an ink jet print head arranged so that ink jets are formed in a cross direction of the continuous web. Specifically, the ink jet printing units (a number of the units is equal to the number of inks used in printing on one side of the continuous web) are arranged at regular intervals in the length direction of the continuous web. Next to this arrangement, other ink jet printing units (a number of the units is equal to the number of inks used in printing the other side of the continuous web) are arranged at regular intervals in the length direction of the continuous web. A continuous web reverse travel mechanism is provided so that a continuous web, that has been guided below an ink jet printing unit for printing one side, is fed above the ink jet printing unit for printing the other side. And then, after it has passed the ink jet printing unit for printing the other side, the guiding direction is reversed. The surface of the continuous web has been turned upside down as a result of this reversing. The continuous web is guided below the ink jet printing unit for printing the other surface. Accordingly, a continuous web is first guided below an ink jet printing unit for printing one side, and that one side is printed, then the continuous web is reversed by the continuous web reverse travel mechanism, and in the turned over state is guided below the ink jet printing unit for printing the other side, and the other side is printed, and after that the travel direction is reversed again and the continuous web is guided outside the continuous web double sided printing unit.
The printing unit for printing on one surface and the other surface of a continuous web of related art 3 is provided with a turn bar for changing the travel direction of a continuous web traveling substantially horizontally through 90 degrees, and also turning over the continuous web and causing it to travel substantially horizontally. The printing unit is provided with ink jet printing units for printing one side of the continuous web being arranged at regular intervals in the travel direction, above the traveling path of the continuous web facing the turn bar. The printing unit is also provided with other ink jet print units for printing the other side of the continuous web being arranged at regular intervals in the travel direction above the traveling path of the continuous web that has passed the turn bar. Accordingly, the continuous web is first made to travel along the travel route of the continuous web facing the turn bar, to print one side, then the continuous web is reversed by the turn bat and in the turned over state made to travel the traveling path of the continuous web that passed through the turn bar to print the other side.
Also, the newspaper manufacturing method of related art 4 is a method in which a plurality of lateral printed rows, having different printing content for each printing line, the lateral printed rows having at least two printed surfaces corresponding to each other on either side of a continuous web in a cross direction of the continuous web, are handled as one print cycle, are repeatedly printed on both sides of the continuous web in a printing direction using a digital printing device, a cut is made for every double sided double spread, and for each lateral printed row, setting is performed for each printing cycle, and for each setting a double spread is folded to produce newspapers of a number of pages corresponding to the number of printing cycles.
In related art 4, as a system for executing the newspaper manufacturing method, a mechanism is disclosed in which a continuous web is supplied from an upstream side of the digital printing device, the continuous web is cut to a specified size at a downstream side of the digital printing device, and the cut sheets are stacked to a specified number and folded.
As disclosed in related art 3, in the current technology it is a precondition for an ink jet print head for printing a continuous web that the ink discharge ports face downwards, and a continuous web that is to be printed on must have a printing surface facing upwards, and be guided underneath the ink jet print head.
However, the related arts the above description have the following problems.
Specifically, the printing unit for printing on one surface and the other surface of a continuous web as disclosed in related art 1 and related art 2 has an ink jet printing unit group for printing one side and an ink jet printing unit group for printing the other side aligned on a substantially horizontal plane and in the same direction, and arranged spaced apart from each other at regular intervals. This gives a printing unit for printing on one surface and the other surface of a continuous web that is long in the arrangement direction, and necessitates a long flat region for installation. Also, the printing unit for printing on one surface and the other surface of a continuous web generally has a supply unit for the continuous web provided at an upstream side and a processing unit for appropriately processing the continuous web after printing arranged at a downstream side, and is used as a ink jet printing system for a continuous web, to carry out printing and post printing processing in a consistent manner, but with such a ink jet printing system for a continuous web the overall length of the system becomes longer, and when a single person carries out continuous operation of monitoring the overall system they must stay alert and must never be absent.
The printing unit for printing on one surface and the other surface of a continuous web disclosed in related art 3 has an ink jet printing unit group for printing one side and an ink jet printing unit group for printing the other side arranged on a substantially horizontal plane but with row directions differing by 90 degrees, and spaced apart at regular intervals, with a turn bar provided between the two ink jet printing unit groups in a state inclined by 45 degrees with respect to the row direction of the ink jet print unit group for printing on the one side, and a continuous web that has passed through the ink jet printing unit group for printing the one side traveling substantially horizontally and been printed on the one side is rotated through 180 degrees on the peripheral surface of the turn bar so as to be turned upside down, and the substantially horizontal traveling direction is changed by 90 degrees to guide the continuous web to the ink jet printing unit group for printing the other side, and the other side is printed. Therefore, the length in one direction is shorter than the printing unit for printing on one surface and the other surface of a continuous web disclosed in related art 1 and related art 2, but is not really that different in total length, and since the ink jet printing unit group for printing one side and the ink jet printing unit group for printing the other side are arranged with arrangement directions 90 degrees different from each other it requires a rectangular flat installation region that is wider than the installation region for the printing unit for printing on one surface and the other surface of a continuous web disclosed in related art 1 and related art 2, where lengths in which at least a group of ink jet printing devices are arranged are taken as two adjacent sides.
Also, the printing unit for printing on one surface and the other surface of a continuous web, similarly to the printing unit for printing on one surface and the other surface of a continuous web disclosed in related art 1 and related art 2, generally has a feed unit for the continuous web and a processing unit for suitably processing the continuous web after printing arranged at an upstream side and a downstream side respectively, and is used as an ink jet printing system for a continuous web for carrying out printing and post printing processing in a consistent fashion. However, with this type of ink jet printing system for a continuous web, it is necessary for a rectangular flat installation space for installation of the entire system to be wider, and when a single person carrying out continuous operations to monitor the overall system they must stay alert and be constantly present.
On the other hand, the newspaper manufacturing method of related art 4 is a method in which a plurality of lateral printed rows, each having different print content, and with each row having at least two printed segments corresponding to each other on both sides of a continuous web in a cross direction of the continuous web, are handled as one print cycle, with repeated printing in a printing direction, a cut is made for every lateral printed row and for every double sided double spread, setting is performed for each printing cycle, and for each setting a double spread is folded to manufacture newspapers of a number of pages corresponding to the number of printing cycles.
Therefore, when a digital printing device has an ink jet printing unit, in printing newspapers of a blanket size (broadsheet), the fact that printing is possible for an advertisement page spanning two whole adjacent newspaper pages, which has recently become common, means it is necessary for the ink jet print heads to be small, and to have a width enabling printing of two newspaper pages that are next to each other in a cross direction, that is, a width in excess 800 mm, but operating such a wide in jet print head with good precision is extremely difficult, and inevitable leads to high costs. Also, printing an advertisement page spanning the whole of two adjacent pages of a newspaper with two ink jet print heads each capable of printing one page of a newspaper is not inconceivable, but installing the ink jet print head to be aligned with good precision, so that there are no streaks remaining such as portions where printing does not occur at the boundaries of printing image using double sided ink jet print heads, or portions where printing has overlapped, is extremely difficult. In addition, in any event maintenance is not simple, and the burden placed on an operator increases with the size of the system or with precision becoming more important. Also, a cut is made for each sideways print line, and for each double spread, which means that also in cases where two or more pages are printed on a continuous web of large paper width, it is difficult to make cuts changing the number of pages arranged for each sideways printing row, it is not possible to obtain a paper space of a single page size, or a large page space where three pages or more are arranged sideways such as in what is called a desired panorama page which there has recently been a demand for, and it is not possible to produce newspapers having a page form with variable folding.